Front tyre fine, back tyre finshed - do i have to replace both?

Hi Guys,

I really need to replace my back tyre. I am planning a ride to Namibia in a couple of months but will be mostly tar. I do however love going off the beaten track where ever possible but living in Joburg this is rarely the case.
I have two questions - is the Heidenau K60 scout an excellent tyre for 50/50 riding ???? And do i need to have the same brand/tread tyre on  the front?

thanks